1. Field of the Invention
The present invention relates generally to a two stroke engine and more specifically to a load responsive fuel supply control arrangement for a multi-cylinder two stroke engine.
2. Description of the Prior Art
JU-A-64-11337 discloses a two cycle engine wherein all of the cylinders are used during high load operation and during low speed/low load modes of operation fuel supply to a selected number of cylinders is cut-off.
During the mode of operation wherein a number of cylinders are deactivated, the blow down effect induced by the exhausting of the combustion gases the amount of fresh air which is inducted into the active cylinders is increased as compared with the amount which is inducted into the deactivated cylinders. Due to this increase in fresh air induction, the amount of fuel which is injected also increases. Accordingly, the ignition and combustion characteristics tend to be maintained.
Further, as a number of cylinders are deactivated the amount of torque which is produced by the engine tends to be reduced. As a result, the throttle valve opening degree is increased and the amount of fresh air which inducted into the active cylinders and the amount of residual combustion gas which tends to be retained in said cylinders tends to be reduced. Accordingly, reliable ignition and stable low load engine operation is achieved.
However, with this type of arrangement, at the time the deactivated cylinders are re-activated, the change to full cylinder operation induces a sudden marked increase in engine torque. Further, during the partial cylinder mode, as the active cylinders are each supplied with fuel every two cycles of the engine, combustion gasses tends not to be adequately exhausted from the combustion chambers and results in the deterioration of the combustion process.